Isolation system and method

ABSTRACT

An isolation system and method are disclosed. The isolation system includes a beam that includes a first end and a second end. The isolation system may include at least one clamping block comprising first elastomeric material, and the first end may be coupled with the first elastomeric material by the at least one clamping block. An end condition of the buckling beam may be varied based on compression stiffening of the first elastomeric material.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/043,369, filed on Aug. 28, 2014, which is incorporated herein byreference in its entirety.

FIELD

The present invention relates to an isolation system and method.

BACKGROUND

In the field of low-frequency vibration and shock isolation, variableperformance is typically achieved through variable damping force,forcing fluid through a variable geometry orifice or changing theviscosity of the fluid as described in, for example, U.S. Pat. No.8,240,439 and U.S. Pat. No. 6,874,603 which are incorporated herein byreference in their entirety. These systems tend to be expensive,temperature sensitive, and offer only limited performance improvement asthey dissipate energy. Fully active isolation systems, as described in,for example, U.S. Pat. No. 8,439,299 which is incorporated herein byreference in its entirety, are also know in the art. Although thesesystems store/release energy, they require sophisticated controlalgorithms and are severely limited by the power, stroke, and bandwidthof the actuator.

Passive negative stiffness isolation, known in the art, consists of anetwork of positive and negative stiffness springs, combined to create anonlinear and hysteretic load path. They are capable of quasi-zerostiffness, even while supporting large loads, ultra-high stiffness, andultra-high hysteretic (structural) damping. However, the negativestiffness isolation is for passive systems, without active tuning oradjustment of the negative side.

An active tuning of positive elements of a negative stiffness system isdescribed in, for example, U.S. Pat. No. 8,132,773 which is incorporatedherein by reference in its entirety. However, it is largely used forthermal compensation.

“Euler columns” Isolators use buckled beams as vibration isolators,however, the supported mass is in parallel with the buckled beam andthis class of isolators is not adjustable as shown in FIGS. 1a-c .“Euler columns” Isolators are further described by WinterFlood et. al.,Classical and Quantum Gravity, October 2002 which is incorporated hereinby reference in its entirety.

In view of the above limitation, an improved isolation system and methodare presently disclosed.

SUMMARY

According to one aspect, an isolation system is presently disclosed. Theisolation system comprising: a buckling beam comprising a first end anda second end; and a first restraining mechanism engaged with thebuckling beam, the first restraining mechanism being configured tovariably control a first restraining condition of the buckling beam andto thereby affect a negative stiffness of the buckling beam.

According to another aspect, a method is presently disclosed. The methodcomprising: adjusting a first restraining mechanism engaged with a beam,the first restraining mechanism being configured to variably control afirst restraining condition of the buckling beam and to thereby affect anegative stiffness of the buckling beam, and wherein the beam comprisesa first end and a second end.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1a-c depict Euler Column Isolator as known in the art.

FIGS. 2a-b depict an isolation system according to some embodiments ofthe present disclosure.

FIGS. 3a-c depict another isolation system according to some embodimentsof the present disclosure.

FIGS. 4a-c depict force displacement relationships generated by anegative stiffness system, according to some embodiments of the presentdisclosure.

FIGS. 5a-c depict buckled mode shapes, according to some embodiments ofthe present disclosure.

FIGS. 6a-c depict force displacement relationship generated by buckledmode shape, according to some embodiments of the present disclosure.

FIG. 7 depicts force displacement generated from finite element analysisby changing the torsion stiffness at the ends of the beams, according tosome embodiments of the present disclosure.

FIGS. 8a-b depict another isolation system according to some embodimentsof the present disclosure.

FIG. 8c depicts another isolation system according to some embodimentsof the present disclosure.

FIGS. 9a-d depict another isolation system according to some embodimentsof the present disclosure.

FIGS. 10a-b depict another isolation system according to someembodiments of the present disclosure.

In the following description, like reference numbers are used toidentify like elements. Furthermore, the drawings are intended toillustrate major features of exemplary embodiments in a diagrammaticmanner. The drawings are not intended to depict every feature of everyimplementation nor relative dimensions of the depicted elements, and arenot drawn to scale.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth toclearly describe various specific embodiments disclosed herein. Oneskilled in the art, however, will understand that the presently claimedinvention may be practiced without all of the specific details discussedbelow. In other instances, well known features have not been describedso as not to obscure the invention.

According to some embodiments, various isolation systems that arepresently disclosed include a continuously variable, high throw,negative stiffness shock and/or vibration isolation system. According tosome embodiments, the negative stiffness is achieved through thebuckling of beams into their lowest energy buckled shape, which iscontrolled by, for example, changing the torsional stiffness of thebeam's boundary conditions. Buckled beams provide a near constantnegative stiffness over a large distance (high throw). According to someembodiments, the amount of high throw negative stiffness of the beams iscontinuously varied by changing the torsional stiffness at the mountingpoints of the beams.

According to some embodiments, various isolation systems that arepresently disclosed create springs with continuously variable springrates. Continuously variable springs have several applications includingvibration isolation, sensor tuning and/or robotic joints. Systems withcontinuously variable spring rates allow the system to perform well overa wider range of conditions relative to systems with fixed spring ratesthat can behave poorly when operated away from their design condition,greatly extending the performance and functionality relative to thepassive state of the art systems. According to some embodiments, variousisolation systems that are presently disclosed provide stiffness changesthat are continuously variable and that can be maintained at constantspring rates over a larger displacement range.

According to some embodiments, various isolation systems that arepresently disclosed can be applied to, for example, transportationsystems that are subject to changing payload weights and/or changinginternal or external vibrations from which the payload is to beisolated. According to some embodiments, various isolation systems thatare presently disclosed can be applied to, for example, car suspensionsand/or engine mounts. According to some embodiments, various isolationsystems that are presently disclosed can be applied to, for example,payloads subject to shocks of different energy levels such as mitigatingpayload damage due to drops from different heights or impacts occurringat different speeds.

Contrary to the prior art, according to some embodiments, variousisolation system(s) presently disclosed provide continuously variablenegative stiffness that can be maintained over large displacements.

According to some embodiments, various isolation systems that arepresently disclosed include two parts: 1) a buckled beam or set of beamsthat produce negative stiffness over a large distance and 2) a variabletorsional stiffness joint or connection between the beams and theprimary structure. According to some embodiments, the joint isadjustable over a range of torsional stiffness either manually or withan actuator. According to some embodiments, the range of torsionalstiffness is either continuously adjustable or have several discretesettings of torsional stiffness. According to some embodiments,isolation system presently disclosed provides continuously variablenegative stiffness, efficiently over greater distances.

An isolation system 100, according to some embodiments presentlydisclosed, is shown in FIGS. 2a-b . According to some embodiments, theisolation system 100 comprises a negative stiffness beam 110 constrainedby one or more hardening springs 120 and clamping blocks 130. Accordingto some embodiments, a payload is placed on the clamping blocks 130 andallowed to move as shown by arrow 140. According to some embodiments,the clamping blocks 130 are coupled to ground and/or a payload by avariable compression system. The ground and/or payload may representcomponents to be isolated, such as a vehicle chassis and an engine, avehicle chassis and one or more wheels, axle, or other suspensioncomponents. According to some embodiments, the variable compressionsystem could be implemented in various ways, such as a screw-drivenclamping device (not shown) or a wedge-driven clamping device (notshown). As the clamping blocks 130 are compressed further together, thespring rate of the springs increases. This results in a variabletorsional stiffness end constraint for the beam 110.

According to some embodiments, the beams used by the presently disclosedisolation system(s) are buckled into a higher mode (e.g., 2, 3, orgreater) in order to produce near constant negative stiffness over largedisplacements.

An isolation system 300, according to some embodiments presentlydisclosed, is shown in FIGS. 3a-c . According to some embodiments, theisolation system 300 comprises one or more beams 310 coupled at bothends of the beams 310 to bases 320, 330. Base 320 may be disposed at afirst end of the beam 310, and base 330 may be disposed at a second endof the beam 310.

According to some embodiments, the center of the beams 310 is coupled toa payload 340 via a payload mount. In other embodiments, the payloadmount may be part of the base 320 or the base 330.

According to some embodiments, the bases 320, 330, and the payload mountinclude restraining mechanisms. According to some embodiments, the bases320, 330 and the payload 340 can move relative to each other in aconstrained path such as the line represented by line 350 as illustratedby the three positions 1, 2 and 3 shown in FIGS. 3a-c . According tosome embodiments, a linear bearing 360 is used to maintain the relativedisplacement path of the payload 340.

According to some embodiments, when the position of the center of thebeams 310 is close enough to the ends of the beams 310 such that thebeams 310 buckle into a higher order mode shape, negative stiffness isgenerated in the region indicated in the force displacement curve shownin FIG. 4a . For example, the beams 310 in positions 1 or 3 as shownFIGS. 3a and 3c are not buckled into a higher mode shape and have apositive stiffness as indicated in FIG. 4a . But when the centralconstraint of the beams 310 is in position 2 as shown in FIG. 3b , it isclose enough to the end constraints to cause enough axial compression tobuckle the beams 310 into their third mode shape and produce thenegative stiffness indicated in FIG. 4a . In some embodiments, thedistance over which the negative stiffness is nearly constant depends onhow close the beams 310's center constraint is to the beams 310's endconstraint, the distance d as shown in FIG. 3a . The shorter thedistance d becomes, the longer the region of near constant negativestiffness as indicated in FIG. 4b . According to some embodiments, theshortest achievable distance d, and hence the largest achievable regionof near constant negative stiffness, is determined by the maximum stressin the beams 310 and its structural limit. On the other hand, if thedistance d is too high, the beams 310 may not generate enough axialcompression to buckle into a higher mode shape. When this happens,negative stiffness is still generated but it is not as constant overlarge distances as shown in FIG. 4 c.

According to some embodiments, changing the torsional stiffness of theboundary conditions where the beam is connected to the base and/or tothe payload changes the amount of negative stiffness. According to someembodiments, for beams with both connection points free to rotate, thebeam buckles into mode shape 1 as shown in FIG. 5a . In someembodiments, for beams with one end free to rotate and the otherclamped, the beam buckles into mode shape 2 as shown in FIG. 5b .According to some embodiments, for beams with both ends clamped, thebeam buckles into mode shape 3 as shown in FIG. 5c . Mode shapes higherthan mode 3 may be achievable by changing the boundary conditions at theconnection points of the beam to the structure. The different amounts ofnegative stiffness that are generated by mode shapes 1, 2 and 3 areshown in FIGS. 6a -c.

According to some embodiments, changing the boundary condition at one orboth of the connection points allows for transition between mode shapesand hence allows the isolation system to continuously vary the negativestiffness. For example, changing the torsional stiffness of theconnection from the end of the beam to the base structure changes thenegative stiffness according to a finite element analysis as shown inFIG. 7. At least some of the presently disclosed embodiments include ameans (e.g., one or more restraining mechanisms) by which to vary thetorsional stiffness where the beam connects to the base and/or to thepayload. The torsional stiffness may be varied continuously or may bevaried between different states. The restraining mechanism for varyingthe torsional stiffness can include, for example, hardening springsand/or compressed rubber that are clamped between two plates where thedistance between the two plates is variable via an actuator such as, forexample, an electric motor connected to a linear drive.

According to some embodiments presently disclosed, variable torsionalstiffness is based on compression stiffening of elastomers as shown inFIGS. 8a-b . The buckling beam 805 is clamped between the elastomericmaterial 810 that exhibits a shear hardening constitutive relationshipwith compression (such as, for example, urethane and/or naturalrubbers). In some embodiments, spacers 815 may be added that arecomposed of a different material, such as, for example, metal (as shownin FIG. 8c ). These spacers may not compress in the same way as theelastomeric material 810, and may therefore provide additional heightwhile allowing for different compression displacement ranges.

According to some embodiments, the thickness of the elastomer and thenumber of layers (and spacers) determine the absolute stiffness, thevariability of the stiffness, and the maximum angular displacementpossible. According to some embodiments, when the distance between thetwo clamping blocks 820 is high then the torsional stiffness will below, allowing for a larger angular displacement of the beam 805 ends asshown in FIG. 8a . According to some embodiments, when the distancebetween the two clamping blocks 820 is small as shown in FIG. 8b thenthe torsional stiffness will be high. Again, using spacers may changethis relationship given that the space between the two clamping blocks820 may be greater while using less elastomeric material to separate theclamping blocks 820.

One or both of the clamping blocks 820 may be moveable. In variousembodiments, the buckling beam 805 may be clamped at one or more of thefirst end of the buckling beam 805, the second end of the buckling beam805, and a midpoint between the first end and the second end.

According to some embodiments, additional hardening can be achieved byplacing the elastomer in a pocket of slightly larger size than theuncompressed material 830 such that the elastomer is restricted fromexpanding to the side after a certain amount of compression, effectivelyincreasing the compressive stiffness. This method for varying stiffnessis described in “Handbook on Stiffness and Damping in Mechanical Design”by Eugene I. Rivin, which is incorporated herein in its entirety.

In some embodiments, the restraining mechanism may include clamps thatare engaged or disengaged. Engaging the clamps may result in a fixed orheld end condition, and disengaging the clamps may result in a pinnedend condition as described in greater detail below.

An isolation system 900, according to some embodiments presentlydisclosed, is shown in FIGS. 9a-d . According to some embodiments, theisolation system 900 comprises one or more beams 910 pinned at itsexternal points and comprising one or more clamping locations 920 adistance z away from ends 930, 935. If the distance z is relativelysmall compared to the length of the beams 910 the effect may be toeffectively change the boundary condition without changing the lengthsubstantially. According to some embodiments, the clamping locations 920can be engaged with a plunging clamp that will apply a fixed or built-intype boundary condition and thus prevent rotation of the beams 910. Thiswill provide a step increase in negative stiffness for a very rigidclamping force and a variable change in negative stiffness for clampssupported by elastic elements (not shown). FIGS. 9b-d depict variationsin the design including, for example, making conic or hemisphericalmounting depressions in the beam, and inverting the contact pairs so athere is protrusion on the beam. According to some embodiments, theisolation system 900 comprises one or more actuators 950. The actuators950 may be, for example, pneumatic and hydraulic, electromagnetic motorsand lead screws, as well as solid state actuators, such as piezoelectricor magnetostrictive actuators. According to some embodiments, theactuator 950 selection depends on the overall stiffness of the beam 910as well as the required travel of the beam 910 which will determine thethrow of the actuator 950 and thus the particular system desired.According to some embodiments, the mechanical stiffness of the actuator950 will affect the stiffness of the isolation system 900. For example,engaging the restraining system may include activating an actuator,which may result in the beam being held by one or more actuators.

The stiffness of the one or more actuators may affect how the isolationsystem 900 behaves.

An isolation system 1000, according to some embodiments presentlydisclosed, is shown in FIGS. 10a-b . According to some embodiments, theisolation system 1000 comprises one or more beams 1010 pinned at itsexternal points and comprising one or more clamping locations 1020 adistance x away from at least one end 1030. According to thisembodiment, the at least one end 1030 is positioned between the clampinglocations 1020 and the beams 1010 as shown in FIGS. 10-b. According tosome embodiments, the clamping locations 1020 can be engaged with aplunging clamp that will apply a fixed or built-in type boundarycondition and thus prevent rotation of the beams 1010. This will providea step increase in negative stiffness for a very rigid clamping forceand a variable change in negative stiffness for clamps supported byelastic elements (not shown). According to some embodiments, theisolation system 1000 comprises one or more actuators 1050. Theactuators 1050 may be, for example, pneumatic and hydraulic,electromagnetic motors and lead screws, as well as solid-state actuatorssuch as piezoelectric or magnetostrictive actuators. According to someembodiments, the actuator 1050 selection depends on the overallstiffness of the beam 1010 as well as the required travel of the beam1010 which will determine the throw of the actuator 1050 and thus theparticular system desired. According to some embodiments, the mechanicalstiffness of the actuator 1050 will affect the stiffness of theisolation system 1000.

At least some embodiments presently disclosed may be implemented ifdiscrete values of negative stiffness are desired as opposed tocontinuously variable negative stiffness.

While several illustrative embodiments of the invention have been shownand described, numerous variations and alternative embodiments willoccur to those skilled in the art. Such variations and alternativeembodiments are contemplated, and can be made without departing from thescope of the invention as defined in the appended claims.

As used in this specification and the appended claims, the singularforms “a,” “an,” and “the” include plural referents unless the contentclearly dictates otherwise. The term “plurality” includes two or morereferents unless the content clearly dictates otherwise. Unless definedotherwise, all technical and scientific terms used herein have the samemeaning as commonly understood by one of ordinary skill in the art towhich the disclosure pertains.

The foregoing detailed description of exemplary and preferredembodiments is presented for purposes of illustration and disclosure inaccordance with the requirements of the law. It is not intended to beexhaustive nor to limit the invention to the precise form(s) described,but only to enable others skilled in the art to understand how theinvention may be suited for a particular use or implementation. Thepossibility of modifications and variations will be apparent topractitioners skilled in the art. No limitation is intended by thedescription of exemplary embodiments which may have included tolerances,feature dimensions, specific operating conditions, engineeringspecifications, or the like, and which may vary between implementationsor with changes to the state of the art, and no limitation should beimplied therefrom. Applicant has made this disclosure with respect tothe current state of the art, but also contemplates advancements andthat adaptations in the future may take into consideration of thoseadvancements, namely in accordance with the then current state of theart. It is intended that the scope of the invention be defined by theClaims as written and equivalents as applicable. Reference to a claimelement in the singular is not intended to mean “one and only one”unless explicitly so stated. Moreover, no element, component, nor methodor process step in this disclosure is intended to be dedicated to thepublic regardless of whether the element, component, or step isexplicitly recited in the claims. No claim element herein is to beconstrued under the provisions of 35 U.S.C. § 112, sixth paragraph,unless the element is expressly recited using the phrase “means for . .. ” and no method or process step herein is to be construed under thoseprovisions unless the step, or steps, are expressly recited using thephrase “step(s) for. . . . ”

What is claimed is:
 1. An isolation system comprising: a buckling beamcomprising a first end and a second end; and a first restrainingmechanism comprising a first hardening spring engaged with the bucklingbeam at the first end; a second restraining mechanism comprising asecond hardening spring engaged with the buckling beam at the secondend, wherein the first restraining mechanism and the second restrainingmechanism are configured to variably clamp the buckling beam to controla first and second restraining condition of the buckling beam and tothereby affect a negative stiffness of the buckling beam.
 2. Theisolation system of claim 1 further comprises a payload mount coupled tothe buckling beam at one of the first end, the second end, and alocation between the first end and the second end.
 3. The isolationsystem of claim 1 wherein the buckling beam is movably pinned at thefirst end; and the first restraining mechanism is engaged or disengagedto control whether the buckling beam has a pinned restraining conditionor a fixed restraining condition at the first end.
 4. The isolationsystem of claim 3, wherein the first restraining mechanism includes anactuator.
 5. The isolation system of claim 3 wherein the buckling beamis movably pinned at the second end, and wherein the second restrainingmechanism is engaged or disengaged to control whether the buckling beamhas a pinned restraining condition or a held restraining condition atthe second end.
 6. The isolation system of claim 3 further comprises apayload mount coupled to the buckling beam.
 7. The isolation system ofclaim 6, wherein the payload mount is allowed to travel between a firstposition and a second position.
 8. The isolation system of claim 6,wherein the first restraining mechanism is positioned between thepayload mount and the first end.
 9. The isolation system of claim 6,wherein the first end is positioned between the payload mount and thefirst restraining mechanism.
 10. An isolation system comprising: abuckling beam comprising a first end and a second end; a firstrestraining mechanism engaged with the buckling beam, the firstrestraining mechanism being configured to variably control a firstrestraining condition of the buckling beam and to thereby affect anegative stiffness of the buckling beam; and a base member coupled tothe second end of the buckling beam, wherein the buckling beam ismovably pinned at the first end, wherein the first restraining mechanismis configured to be engaged or disengaged to control whether thebuckling beam has a pinned restraining condition or a fixed restrainingcondition at the first end, and wherein the first restraining mechanismincludes a clamp and a hardening spring between the clamp and the firstend of the buckling beam.
 11. A method comprising: adjusting a firstrestraining mechanism comprising a first hardening spring engaged with afirst end of a buckling beam; and adjusting a second restrainingmechanism comprising a second hardening spring engaged with a second endof the buckling beam, wherein the first restraining mechanism and thesecond restraining mechanism are configured to variably clamp thebuckling beam to control a first restraining condition and a secondrestraining condition of the buckling beam and to thereby affect anegative stiffness of the buckling beam.
 12. The method of claim 11,wherein adjusting the first restraining mechanism comprises: engaging ordisengaging the first restraining mechanism to control whether thebuckling beam has a pinned restraining condition or a held restrainingcondition at the first end.
 13. A method comprising: adjusting a firstrestraining mechanism engaged with a buckling beam, the firstrestraining mechanism being configured to variably clamp the bucklingbeam to control a first restraining condition of the buckling beam andto thereby affect a negative stiffness of the buckling beam, wherein thebeam comprises a first end and a second end, wherein adjusting the firstrestraining mechanism comprises: moving at least one moveable clampingblock comprising a first elastomeric material, wherein the first end iscoupled with the first elastomeric material by the at least one clampingblock, and wherein a negative stiffness of the buckling beam is variedbased on compression stiffening changes of the first elastomericmaterial caused by position changes of the at least one moveableclamping block.